Re: Kamm tails and drag

["Todd Schinell" <alfatodd@xxxxxxxxxxx>]

I noticed the VW experimental car which gets 300+ mpg and has a drag
coefficient of 0.159 also has a Kamm tail.  The most aerodynamic production
car, the Honda Insight comparitively has a 0.26 coefficient.  You can see
the Kamm tail in the 3rd image down here:
http://www.benerridge.freeserve.co.uk/economy.htm

----- Original Message -----
From: "C M Smith" <cmsmith@domain.elided>
To: <alfa@domain.elided>
Sent: Saturday, April 12, 2003 10:56 PM
Subject: Kamm tails and drag


> I thought the Kamm tail effect resulted from the fact that the Kamm tail
> caused the tail to drag a blob of turbulent air behind the tail that
> approximated the airflow of the long tailed tear drop shape previously
> thought to be ideal, which reduced skin drag due to air to air friction
> being lower than air to bodywork friction. The increase in efficiency is
> due to the reduction in skin drag resulting from the chopped tail and the
> fact that air to air friction is lower than air to bodywork friction of
the
> long tail version. Certainly Porsche experimented successfully with the
> long tail Le Mans design that also had a Kamm tail but further back along
> the ideal teardrop shape. I do not think that turbulence associated with
> tear drop shape could be a factor since the tear drop has very little
> turbulence associated with it. Skin drag is a huge factor at high speeds.
> Turbulence drag is a problem at low speeds also, hence the amount of money
> devoted to reducing turbulence drag from door mirrors and rain gutters to
> cite two mundane examples.
>
> cheers etc
> Michael Smith
> White 1991 164L
> Original owner
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